Question

Stacy bought a skateboard at a local sporting goods store. The skateboard was on sale for 10% off the original price. The store then charges 10% sales tax.
a. how does the original price compare to the final price?
b. would the final price be different if the 10% sales tax was added first and then the 10% discount was applied to this new amount

Answer 1

If the original price is x, then x-0.10x=0.9x (which is a 10 percent off discount - 10 percent = 0.10 if you move the decimal spot 2 places over), then 10% of 0.9x is not 0.10x due to that 0.1/0.9=1/9, not 1/10. 1/10 of 0.9 is 0.09, so
 0.9-0.09=0.81 of the original price

If the 10% sales tax was added first, it wouldn't matter since you're still getting 10% twice either way